1. Field of the Invention
The present invention relates to a contact structure and a manufacturing method thereof, especially to a contact structure having a compliant bump and a test pad and a manufacturing method thereof.
2. Description of Related Art
In the field of forming the integrated circuits (IC) of high density, chips need physical structures and electrical structures that are highly reliable. In order to manufacture within a micro area IC structures of high density, such as liquid crystal panels of high resolution, the control IC used for driving also needs to be closely arranged. Hence, the metal bump on the wafer is used as the conductive contact to serve the purpose.
The U.S. Pat. No. 5,707,902 discloses a bump structure mainly constituted by three film layers (metal layer-polymer layer-metal layer). Since the bump structure includes two metal layers, the depth thereof is so thick that it is difficult to control the evenness of etching. As a result, bump structures with fine line distances cannot be successfully made.
Further, the bump structure disclosed in the U.S. Pat. No. 5,508,228 has a top surface narrower than its bottom surface. After the metal layer is formed on the bump structure, a probe is used to contact the metal layer on the bump structure so as to proceed with an electrical test. However, given that the top surface of the bump structure is narrower than the bottom surface thereof, when the electrical test is performed, the probe usually slides off causing the electrical test to fail.